The invention relates to an arrangement comprising a hollow shaft, an input or drive shaft partially contained in the hollow shaft, and a clamping device. The clamping device has a loose state in which the hollow shaft and the input shaft are removable from each other, and a fixed state in which the hollow shaft is connected to the input shaft.
Arrangements of the type in question are used, for example, in order to connect an output side of a gearing to an input shaft. Typically here, the hollow shaft is connected to the gearing such that a torque can be transmitted between the gearing and the hollow shaft. The input shaft is typically designed as a solid shaft.
The clamping device serves for frictionally connecting the hollow shaft to the input shaft such that a torque can also be transmitted between the hollow shaft and the input shaft. For the installation, the clamping device has a loose state in which the input shaft and the hollow shaft are not yet fixed relative to each other, and therefore the input shaft can be inserted into the hollow shaft. Subsequently, the clamping device is typically transferred into the fixed state, and therefore the hollow shaft is frictionally connected to the input shaft. The two shafts are therefore fixed with respect to each other.
A known arrangement is shown, for example, in DE 742 39 87 U. The hollow shaft here is clamped onto the input shaft by means of a press ring, wherein the diameter of the hollow shaft is uniformly tapered over the circumference thereof. The hollow shaft is also pressed tangentially here.
A further embodiment is shown in DE 42 30 941 A1, wherein it is proposed to provide the hollow shaft with an internal cone on both sides and to compensate for a tolerance between hollow shaft and input shaft via an additional conical and slotted adaptor piece. In this case, an axial offset may occur between the shafts during the transition of the clamping device into the fixed state.
A further embodiment is shown in DE 100 600 37 C1 in which it is proposed to provide the hollow shaft on two sides with an internal cone and to compensate for a possible tolerance between the shafts via an additional conical and slotted adaptor piece. For this purpose, however, an increased number of elements and space during the installation are required.
The invention is based on the object of providing an arrangement in which tolerances of a largest possible size between input shaft and hollow shaft can be compensated for, wherein this is preferably intended to take place as simply as possible and with as little space as possible being required.
The invention achieves the object by an arrangement according to embodiments of the invention.
The invention relates to an arrangement comprising a hollow shaft, an input shaft or drive haft partially contained in the hollow shaft, and comprising a clamping device. The clamping device has a loose state in which the hollow shaft and the input shaft are removable from each other. The clamping device furthermore has a fixed state in which the hollow shaft is connected to the input shaft.
According to the invention, during the transition from the loose into the fixed state, the clamping device introduces forces which are directed radially to the hollow shaft into the hollow shaft at at least three discrete introduction points arranged along a circumference of the hollow shaft such that the hollow shaft bends in the direction of the input shaft at the introduction points and bends away from the input shaft between the introduction points.
The effect which is therefore achieved is that the hollow shaft is no longer subjected tangentially to a compressive stress, but rather predominantly to a bending stress. This permits a significantly more extensive deformability of the hollow shaft, for which less force is also required than in the case of an embodiment according to the prior art in which the hollow shaft is subjected tangentially to a compressive stress. At the same time, self centering is achieved. There is also no necessity to provide slots for bridging high fitting tolerances. Forces are directly transmitted without an additional adaptor piece, with torsional strength and torsional rigidity being maintained.
The introduction points are those points along the circumference of the hollow shaft at which the hollow shaft absorbs forces directed radially to the hollow shaft and accordingly bends toward the input shaft. Said forces are preferably distributed uniformly over the circumference of the hollow shaft. Furthermore preferably, precisely three introduction points are involved here, as a result of which a secure connection is made possible between the shafts and at the same time respective circumferential portions, which are available for the bending, between the introduction points are as long as possible.
The hollow shaft bends away from the input shaft between the introduction points such that the radial distance in respective regions between the introduction points is larger than the radial distance between the hollow shaft and the input shaft in the loose state of the clamping device. Said regions run along the circumference of the hollow shaft and do not take up the entire circumferential portion between two circumferentially adjacent introduction points because the hollow shaft bears against the input shaft adjacent to the introduction points.
The arrangement according to the invention can be provided or designed, for example, for connecting the hollow shaft of a gearing to the input shaft or output shaft of a system/machine.
The hollow shaft is designed in particular to guide the force, which is introduced radially by means of the clamping device, by a purely radial flow of force, i.e. in particular free from tangential and/or axial force components, through the hollow shaft directly radially into a radially aligned clamping point between hollow shaft and input shaft. In other words, the radial force introduced by the clamping device is passed on radially by the hollow shaft and acts radially or normally on the input shaft, i.e. introduction of force preferably does not bring about any tangential and/or axial forces in the hollow shaft. The introduction points preferably lie directly over the clamping point, i.e. are precisely fixed geometrically.
The force results from the elastic deformation brought about by means of the clamping device, wherein the elastic energy stored in the hollow shaft opposes the clamping forces, for which reason the hollow shaft is of deformable design. So that the hollow shaft does not obstruct said clamping operation, the hollow shaft is preferably designed to be deformable polygonally.
The clamping device is not involved in the transmission of the shaft torque itself.
A material thickness of the hollow shaft can vary over the circumference of the hollow shaft, i.e. an external contour of the hollow shaft can differ from an internal contour of the hollow shaft. The material thickness of the hollow shaft can vary over the circumference in such a manner that the material thickness has a respective local maximum at the at least three introduction points.
In a corresponding manner, a material thickness of an adaptor sleeve can vary over the circumference of the adaptor sleeve, i.e. an external contour of the adaptor sleeve can differ from an internal contour of the adaptor sleeve. The material thickness of the adaptor sleeve can vary over the circumference in such a manner that the material thickness has a respective local maximum at the at least three introduction points.
A plurality of possible embodiments of the arrangement according to the invention and, where applicable, respective variants of said embodiments are described below.
According to a first embodiment, the clamping device is designed as a clamping ring which has a conical bore. Furthermore, the clamping device is arranged in an axially displaceable manner relative to the hollow shaft such that, during the transition from the loose into the fixed state, said clamping device presses the hollow shaft radially inward by means of the conical bore at the introduction points.
This embodiment permits the necessary forces, which are directed radially to the hollow shaft, to be produced at the introduction points by means of an axial movement of the clamping ring. Such an axial displacement can be achieved, for example, by axially arranged screws. It is therefore possible to produce considerably higher forces on the hollow shaft using relatively little effort for rotating a screw.
The clamping ring is preferably designed as a closed clamping ring. This increases the stability of the clamping ring. Such an embodiment as a closed clamping ring is possible because, in the embodiment according to the invention, the clamping ring does not have to change its circumference.
According to a first variant of the first embodiment, the hollow shaft has an external profile which, at the introduction points, has a respective radially outwardly directed elevation which is of conical design in the axial direction. Said elevations define the position of the introduction points. The formation of such elevations on the hollow shaft permits the introduction points to be defined by the shaping of the hollow shaft.
The elevations can be of polygonal design, which can mean, for example, that said elevations have, a cross section which is rectangular or trapezoidal. It should be mentioned that, in the case of such a rectangular or trapezoidal shape or also in the case of another polygonal shape or other shape, one side of the respective elevation merges into the encircling clamping ring which is circular in cross section. Alternatively to an elevation of polygonal design, the elevation can also be designed, for example, in such a manner that an external diameter of the hollow shaft is increased continuously toward a respective introduction point, and therefore the respective elevation does not have any recognizable edges.
According to a second variant of the first embodiment, an encircling adaptor piece is arranged between the clamping device and the hollow shaft, which adaptor piece has a thickness profile designed in such a manner that, at least in the fixed state of the clamping device, said adaptor piece transmits a radial force between the clamping device and the hollow shaft at the introduction points. This makes it possible to define the positions of the introduction points by means of the adaptor piece. The thickness profile can be designed, for example, in such a manner that the adaptor piece has a number of projections on the outside, as has been described with respect to the first variant. To this extent, reference is made here to these embodiments.
According to a third variant of the first embodiment, the hollow shaft has a respective external key slot at each introduction point, wherein a plurality of keys is provided between the clamping device and the hollow shaft. Each key is contained here in a respectively assigned key slot and, at least in the fixed state of the clamping device, transmits a radial force between the clamping device and the hollow shaft at the introduction points.
This embodiment with keys makes it possible, for example, to provide different keys for different installation purposes, for example keys made of different material or with a different shaping. The keys here can preferably be of conical or wedge-shaped design. In addition, they can be exchanged after a certain operating period of the arrangement in order to avoid a deterioration in the strength of the connection between the hollow shaft and the input shaft or in order to restore the original quality of the connection after a determined deterioration in said connection.
In the case of all three variants of the first embodiment, forces directed radially to the hollow shaft are produced at the introduction points by means of the conical bore of the clamping ring by the clamping ring being displaced axially in such a manner that the conical bore tapering at a certain axial position comes into engagement with another element, for example an elevation or a key, and presses said element radially in the direction of the hollow shaft.
An external profile which contains said elements is preferably of conical design here. This permits a particularly good fit between the conical bore of the clamping ring and the conically designed external profile of the hollow shaft, of the adaptor piece or of the keys. Furthermore preferably, a slope of the cone of the external profile corresponds to a slope of the cone of the clamping ring.
Hollow shafts or adaptor pieces for the first embodiment, as described, can be obtained for example, by out-of-round turning. A surface of a round workpiece can therefore be structured along the circumference in a known manner.
According to a second embodiment, the hollow shaft has an external profile which, at the introduction points, has a respective radially outwardly directed elevation. The clamping device here is designed as a clamping ring which is rotatable concentrically relative to the hollow shaft and has a plurality of internal depressions in each case assigned to an elevation of the hollow shaft. The depressions have a respective surface profile which is variable along a circumference of the clamping ring such that the respectively assigned elevation is pressed radially inward when the clamping ring is rotated in one direction and is released when the clamping ring is rotated in the opposite direction.
With such an embodiment, instead of the axial displacement of the clamping ring described in the first embodiment, the transition between loose and fixed state of the clamping ring is achieved by rotation of the clamping ring. A space requirement necessary fir the axial displacement and for the actuation of a mechanism for the axial displacement, for example a screw, in the axial direction is therefore superfluous. In other words, in the second embodiment, the clamping ring can be transferred from the loose into the fixed state and vice versa without additional space for this purpose being necessary in the axial direction. This can facilitate the fitting under confined space conditions.
With regard to the elevations mentioned within the scope of the second embodiment, reference should be made to the embodiments of the elevations in the first embodiment that apply analogously here. The elevations in the case of the second embodiment are preferably designed in such a manner that they can be easily pressed radially inward by the depressions when the clamping ring is rotated in a corresponding direction. For this purpose, said elevations can be, for example, of polygonal, in particular rectangular design in cross section, or alternatively can also be of bent design in an appropriate shape.
According to a third embodiment, the clamping device has a plurality of radially adjustable jaws, wherein one jaw in each case is assigned to an introduction point for introducing a force, which is directed radially to the hollow shaft, into the hollow shaft. In the preferred embodiment with three such jaws, a conventional three-jaw chuck can be used. This permits the use of a known device with which, as is known, high radical forces can be produced.
According to a fourth embodiment, the clamping device is designed as a clamping ring with a plurality of radially adjustable screws, wherein one screw in each case is assigned to an introduction point for introducing a force, which is directed radially to the hollow shaft, into the hollow shaft. The screws here are preferably arranged in such a manner that they extend radially with the longitudinal direction thereof transversely with respect to the outer surface of the hollow shaft. In this fourth embodiment, the required forces can be exerted at the introduction points by screwing in the screws. This makes it possible to produce the threes by rotating screws, which makes high forces possible with comparatively little effort.
In the fourth embodiment, there is preferably a number of webs for fixing the clamping ring on the hollow shaft. Said webs are preferably formed in an encircling intermediate space between the hollow shaft and the clamping ring. They can protrude, for example, from the hollow shaft or from the clamping ring. Alternatively, they can be pushed as independent components between the hollow shaft and the clamping ring. The effect can therefore be achieved that, during the installation operation, before the screws are screwed in and tightened, the clamping ring remains concentric with the hollow shaft without said clamping ring having to be held in such a position manually or by aids. This facilitates the installation and ensures that, by uniformly tightening the screws, uniform forces can be produced at the respective introduction points. Respective webs are preferably formed here at or directly adjacent to the introduction points.
According to a first variant of a fifth embodiment, the clamping device has the following: an externally double-conical, internally cylindrical internal ring, an external ring which is arranged at a distance in the radial direction with respect thereto and is of closed and internally double-conical design, and double-conical pressure rings which are inserted on both sides between internal ring and external ring and are clampable against the internal ring and external ring via screws, wherein at least one of the pressure rings has a plurality of projections assigned in each case to an introduction point. As an alternative thereto, in a second variant of the fifth embodiment, the internal ring can also be designed in such a manner that it exerts a radially inwardly directed force on the hollow shaft merely at the introduction points.
In the fifth embodiment, by means of the special design of the clamping device, a particularly uniform effect of the respective forces is achieved in the axial direction via a respective section.
The arrangement can be configured in such a manner that that part of the hollow shaft which bends away from the input shaft between the introduction points is supported on the clamping device.
In all of the embodiments described, with the exception of the first variant of the first embodiment, the hollow shaft preferably has a cylindrical external profile. An as uniform as possible effect of the forces axially is therefore achieved. The designation “cylindrical” is not inevitably understood here as meaning that the respective external profile is completely unstructured, i.e. corresponds in the mathematical sense to the external profile of a cylinder. On the contrary, this designation is understood here as meaning that the respective external profile is not conical, i.e. has a cross section which is non-variable at least in sections in the axial direction. However, it may nevertheless be structured along the circumference, for example by the provision of elevations, keys, grooves or the like.